Aerostatic lighter-than-air airships have seen substantial use since 1783 following the first successful manned flight of the Montgolfier brothers' hot air balloon. Numerous improvements have been made since that time, but the design and concept of manned hot air balloons remains substantially similar. Such designs may include a gondola for carrying a pilot and passengers, a heating device (e.g., a propane torch), and a large envelope or bag affixed to the gondola and configured to be filled with air. The pilot may then utilize the heating device to heat the air until the buoyant forces of the heated air exert sufficient force on the envelope to lift the balloon and an attached gondola. Navigation of such an airship has proven to be difficult, mainly due to wind currents and lack of propulsion units for directing the balloon.
To improve on the concept of lighter-than-air flight, some lighter-than-air airships have evolved to include propulsion units, navigational instruments, and flight controls. Such additions may enable a pilot of such an airship to direct the thrust of the propulsion units in such a direction as to cause the airship to proceed as desired. Airships utilizing propulsion units and navigational instruments typically do not use hot air as a lifting gas (although hot air may be used), with many pilots instead preferring lighter-than-air lifting gases such as hydrogen and helium. These airships may also include an envelope for retaining the lighter-than-air gas, a crew area, and a cargo area, among other things. The airships are typically streamlined in a blimp- or zeppelin-like shape, which, while providing reduced drag, may subject the airship to adverse aeronautic effects (e.g., weather cocking, a.k.a. wind cocking).
Airships other than traditional hot air balloons may be divided into several classes of construction: rigid, semi-rigid, non-rigid, and hybrid type. Rigid airships typically possess rigid frames containing multiple, non-pressurized gas cells or balloons to provide lift. Such airships generally do not depend on internal pressure of the gas cells to maintain the shape of the airships. Semi-rigid airships generally utilize some pressure within a gas envelope to maintain the shape of the airships, but may also have frames along a lower portion of the envelope for purposes of distributing suspension loads into the envelope and for allowing lower envelope pressures, among other things. Non-rigid airships typically utilize a pressure level in excess of the surrounding air pressure in order to retain their shape, and any load associated with cargo carrying devices is supported by the gas envelope and associated fabric. The commonly used blimp is an example of a non-rigid airship.
Hybrid airships may incorporate elements from other airship types, such as a frame for supporting loads and an envelope utilizing pressure associated with a lifting gas to maintain its shape. Hybrid airships also may combine characteristics of heavier-than-air airship (e.g., airplanes and helicopters) and lighter-than-air technology to generate additional lift and stability. It should be noted that many airships, when fully loaded with cargo and fuel, may be heavier than air and thus may use their propulsion system and shape to generate aerodynamic lift necessary to stay aloft. However, in the case of a hybrid airship, the weight of the airship and cargo may be substantially compensated for by lift generated by forces associated with a lifting gas such as, for example, helium. These forces may be exerted on the envelope, while supplementary lift may result from aerodynamic lift forces associated with the hull.
A lift force (i.e., buoyancy) associated with a lighter-than-air gas may depend on numerous factors, including ambient pressure and temperature, among other things. For example, at sea level, approximately one cubic meter of helium may balance a mass of approximately one kilogram. Therefore, an airship may include a correspondingly large envelope with which to maintain sufficient lifting gas to lift the mass of the airship. Airships configured for lifting heavy cargo may utilize an envelope sized as desired for the load to be lifted.
Landing and securing a lighter-than-air airship may also present unique problems based on susceptibility to adverse aerodynamic forces. Although many lighter-than-air airships may perform “vertical takeoff and landing” (VTOL) maneuvers, once such an airship reaches a point near the ground, a final landing phase may entail ready access to a ground crew (e.g., several people), environment monitoring systems, and/or a docking apparatus for tying or otherwise securing the airship to the ground. Without access to such elements, the airship may be carried away by wind currents or other uncontrollable forces while a pilot of the airship attempts to exit and handle the final landing phase. Therefore, systems and methods enabling landing and securing of an airship by one or more pilots may be desirable.
Due to the various features of airships, such as adaptability in takeoff/landing abilities, lifting capacity, and maneuverability, there are many potential uses of airships. For example, airships may be particularly suitable for transporting cargo. Other options for transporting cargo, especially heavy cargo, have limitations. In particular, airplanes, and vehicles, and ships may require certain infrastructures and/or environmental conditions (e.g., runways, roads, waterways, etc.), while airships, with VTOL and hovering capabilities, have greater flexibility to receive, transport, and deliver cargo to a variety of different locations. Thus, an airship that is adapted for a variety of transport functions is desirable.
Further, in order to accommodate these and other potential uses of airships, it is necessary to incorporate various controls that allow the airship to perform certain operations, such as a hover operation. In one example, an airship may approach a landing area, hover near the landing area, perform an operation (e.g., exchange cargo), and depart from the hovering position. It may be difficult, however, for a pilot to consistently and easily maintain the airship in a particular hovering position, because the aerodynamic forces on a hovering airship may widely vary depending on the conditions at the time. Factors such as wind speed, wind direction, wind frequency, turbulence conditions, airship weigh and balance, airship heading etc., and the consideration of these factors may cause operation of the airship to be complicated during hovering (as well as approach and departure). Thus, systems and methods for improved flight planning and easing control of an airship, and particularly an airship during a hovering maneuver, are desirable.
The present disclosure is directed to addressing one or more of the desires discussed above utilizing various exemplary embodiments of an airship.